package shujvjiegou.week7;

import java.util.*;

public class t1 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String str = scanner.nextLine();
        Map<Integer, Integer> map_count = new HashMap<>();
        int num;
        List<Integer> list = new ArrayList<>();
        for (int i = 0; i < str.length(); i++) {
            num = str.charAt(i);
            list.add(num);
            if (map_count.containsKey(num)) {
                map_count.put(num, map_count.get(num) + 1);
            } else {
                map_count.put(num, 0);
            }
        }
        int position = 0;
        int temp = map_count.get(list.get(0));
        for (int i = 0; i < map_count.size(); i++) {
            if (map_count.get(list.get(i)) > temp) {
                temp = map_count.get(list.get(i));
                position = i;
            }
        }
        if (map_count.get(list.get(position)) > str.length() / 2) {
            System.out.println(list.get(position) + "");
        } else {

        }
    }
}
